The Great Orion Nebulain Mapped Color

About This Photograph

The Great Orion Nebula is a vast region of intense star formation. Massive, hot young stars — destined to lead short lives due to the rate at which they are consuming their hydrogen fuel — are the illuminating sources for the clouds of gas and dust that we see. Their intense ultraviolet light excites individual atoms in the nebula, causing them to fluoresce: each chemical element re-emits light in its own specific color.

In this image, special filters were used to isolate the light from three of these elements, and these exposures were then combined to form a color composite: red for sulphur, green for hydrogen, and blue for oxygen. In reality, both sulphur and hydrogen emit a deep red color, while oxygen emits a teal hue. The "mapped" color assignment in this image highlights the distribution of energized atoms in the nebula.

Technical Details

Optics:

14" f/10 RCOS Ritchey-Chrétien Cassegrain.

Mount:

Astro-Physics AP1200GTO.

Camera:

STL-11000XM.

Filters:

Custom Scientific 5nm S-II, H-alpha, O-III.

Dates/Times:

19, 27 January 2004.

Location:

my backyard observatory in Austin, Texas.

Exposure Details:

S-II: 2 hours.H-alpha: 3.5 hours.O-III: 2 hours.

Processing:

To generate the color, the three emission-line images were first histogram-normalized, so that they each covered the same total range of brightness. These were then combined into an RGB image, and finally the H-alpha data was used for the luminance (brightness data).